SHALLOW-WATER FAUNA. 



41 



On the same piece of stone there will most 

 probably be found several twisted or coiled tubes 

 of lime, formed by a little Sea-worm called 

 Serpula. When living in the water the head of 

 this worm projects from its shell and expands 

 a circlet of delicate tentacles, by means of which 

 the food is brought to the mouth. One of these 

 tentacles is specially modified and enlarged at 

 the extremity to forjD^sTconical knob, which, 



FIG. 12. Xauplius larva of a Balanus, enormously magnified. 



when the animal is retracted into the shell, closes 

 the aperture like a stopper. 



Then there may be found some spherical or 

 lobate masses of a fleshy consistency, white, pale 

 pink or yellow in colour, and studded with 

 numerous star-shaped apertures. When these 

 are allowed to remain in a basin of fresh sea- 

 water for some time, each one of the star-like 

 apertures opens, and a beautiful transparent little 



